Many have tried it (as well as the oft-recommended micropayments idea) and it never justifies the added expense and overhead of the customization. Closest is probably the NYTimes’ gift article feature.
Probably true, it's more likely that it's a variation on "there are only a small percentage of people willing to pay any amount of money for an article, so if we offer one-time options, a large enough percentage of people who would have otherwise subscribed with recurring revenue instead pay one-time so their lifetime value is lower"